i hgave heard that it is better to put it on when the grass is wet because the fertilizer sticks to the grass much better, however i would be cautious when rain is in the forecast because it could wash it right back off, best to schedule for after the rain when there is no rain in the forecast.

Fertilizers are salts. Salts draw moisture. Fertilizer dust or liquid fert can draw moisture out of grass leaves, causing a burn and consequent browning of the leaves. Years ago when big green mostly used tanker trucks, I saw many a burned lawn in the summer.

But right now it would likely be OK for brian in SD to apply to wet leaves, especially if more rain is coming to wash it off of leaves. It is usually the high N apps in warmer summer days that will give the noticeable burn.

But if the grass is that wet, you are probably going to muck up the gate and impeller on your spreader, causing a poor and erratic distribution and flow rate.